{ bundlerEnv, ruby, stdenv, katex-server }:

let
  gems = bundlerEnv {
    inherit ruby;

    name = "render-test";
    gemfile = ./Gemfile;
    lockfile = ./Gemfile.lock;
    gemset = ./gemset.nix;
  };
in
  stdenv.mkDerivation {
    name = "katex-converter";
    src = ./convert.rb;
    buildInputs = [ katex-server gems ruby ];
    unpackPhase = "echo 'Skipping unpack phase (nothing to unpack)'";
    installPhase = ''
      mkdir -p $out/{bin,share/katex-converter}
      cp $src $out/share/katex-converter/convert.rb
	cat > $out/bin/katex-converter <<EOF
#!/bin/sh -e
${katex-server}/bin/katex-server &
server_pid=\$!
sleep 1
${gems}/bin/bundle exec ${ruby}/bin/ruby $out/share/katex-converter/convert.rb \$@
kill -KILL \$server_pid
EOF
      chmod +x $out/bin/katex-converter
    '';
  }